Multi-planar locking mechanism for bone fixation

Abstract

A locking mechanism for locking a rod to a bone member. The locking mechanism includes a bone fixation member for attachment to the bone member, the bone fixation member having a spherical portion; an inner housing member having a channel for receiving the rod and having a spherical portion for engaging the spherical portion of the bone fixation member; and an outer housing member for locking the inner housing member to the rod and the spherical portion of the bone fixation member.

We claim: 
     
       1. A locking mechanism for locking a rod to a bone member; said locking mechanism comprising: (a) a bone fixation member for attachment to the bone member, said bone fixation member having a spherical portion;   (b) an inner housing member having a channel for receiving the rod and having a spherical portion for engaging said spherical portion of said bone fixation member; and   (c) an outer housing member for locking said inner housing member to the rod and said spherical portion of said bone fixation member; said outer housing member including a unitary body for positioning about at least a portion of said inner housing member intermediate said channel and said spherical portion of said inner housing member and for simultaneously applying pressure to said inner housing member adjacent said channel and adjacent said spherical portion of said inner housing member for clamping said inner housing member to the rod and to said spherical portion of said bone fixation member.   
     
     
       2. The locking mechanism of claim 1 in which said inner housing member includes a unitary body having a first end, a second end, and a substantially cylindrical outer surface, said outer surface of said body of said inner housing member being tapered between said first and second ends thereof; and in which said body of said outer housing member has a first end, a second end, and a substantially cylindrical passageway therethrough for slidably receiving said body of said inner housing member; said passageway of said body of said outer housing member being tapered between said first and second ends thereof. 
     
     
       3. The locking mechanism of claim 2 in which said spherical portion of said bone fixation member includes a head portion having a substantially spherical outer surface; and in which said body of said inner housing member has a cavity in said second end thereof with a substantially spherical surface for defining said spherical portion thereof and for receiving said substantially spherical outer surface of said head portion of said bone fixation member. 
     
     
       4. The locking mechanism of claim 3 in which said body of said inner housing member has a slot communicating with said cavity thereof for allowing said body of said inner housing member to be compressed about said substantially spherical outer surface of said head portion of said bone fixation member when said body of said inner housing member is received in said passageway of said body of said outer housing member. 
     
     
       5. The locking mechanism of claim 3 in which said body of said inner housing member has a slot communicating with said channel thereof for allowing said body of said inner housing member to be compressed about said rod when said body of said inner housing member is received in said passageway of said body of said outer housing member. 
     
     
       6. The locking mechanism of claim 2 in which said bone fixation member includes a bone attachment portion adapted to be attached to the bone member. 
     
     
       7. The locking mechanism of claim 6 in which said bone attachment portion of said bone fixation member includes external bone screw threads adapted to be screwed into the bone member. 
     
     
       8. The locking mechanism of claim 2 in which said first end of said outer housing member has a channel extending thereacross for receiving the rod. 
     
     
       9. The locking mechanism of claim 2 in which said body of said outer housing has an outer surface with an opening therein for use in forcing said body of said inner housing member into said passageway of said body of said outer housing member. 
     
     
       10. In combination, an elongated rod and a multi-planar locking mechanism for locking said rod to a vertebra; said locking mechanism comprising: (a) a bone screw for attachment to the vertebra, said bone screw including a bone screw thread portion adapted to be screwed into the vertebra and including a head portion attached to the bone screw thread portion; said head portion having a substantially spherical outer surface;   (b) an inner housing member including a body having a first end, a second end, and a substantially cylindrical outer surface; said outer surface of said body of said inner housing member being tapered between said first and second ends thereof; said first end of said body having a channel extending thereacross receiving said rod; said second end of said body having a cavity receiving said head portion of said bone screw; said cavity having a substantially spherical surface that substantially matches a portion of said substantially spherical outer surface of said head portion of said bone screw; said body of said inner housing member having a slot communicating with said cavity and said channel thereof; and   (c) an outer housing member locking said inner housing member to said rod and said head portion of said bone screw; said outer housing member comprising a one-piece, integral body having a substantially cylindrical passageway in which said body of said inner housing member is slidably received, a first end applying pressure against said first end of said body of said inner housing member to compress said first end of body of said inner housing member against said rod to lock said rod to said inner housing member, and a second end applying pressure against said second end of said body of said inner housing member to compress said second end of said body of said inner housing member about said head portion of said bone screw to lock said head portion of said bone screw to said inner housing member; said passageway of said body of said outer housing member being tapered between said first and second ends of said body of said outer housing for causing said body of said inner housing member to be compressed about said substantially spherical outer surface of said head portion of said bone screw and about said rod when said body of said inner housing member is received in said passageway of said body of said outer housing member so that said bone screw and said rod are locked to said inner housing member.